An Historical Summary of Angelic Hierarchies from Part VII: The “Seven” Thrones in In Operibus Sigillo Dei Aemeth by David Richard Jones.

“These days, which abide in the interior light, may be taken for the angelic spirits, and the months, for their orders and dignities. For every single spirit, in that he shines, is a ‘day,’ but as they are distinguished by certain set dignities, so that there are some that are Thrones, some Dominions, some Principalities, and some Powers, according to this distribution of ranks, they are entitled ‘months.’

Moralia I:I:iv — Pope St. Gregory I” [via]